The movements and systems of motility active during fertilization will be studied in living gametes and zygotes by time lapse video microscopy, and with transmission and scanning electron microscopy. The characteristics of sperm incorporation will be investigated using differential interference optics and SEM on denuded eggs and isolated egg surfaces. The characteristics of the formation of the sperm aster and the accompanying pronclear migrations will be recorded in living zygotes and examined by thin section TEM. The role of microfilamentmediated motility during sperm incorporation will be determined by the use of microfilament assembly in hibitors such as cytochalasin B, whereas the role of microtubule polymerization will be investigated using microtubule poisons such as colcemid and griseofulvin. The results will demonstrate the mechanisms whereby the sperm and egg nuclei are brought together during a successful fertilization.